To　achieve　the　“dual　carbo”　goal　and　transition　towards　a　sustainable　energy　system,　establishing　appropriate　electricity　pricing　mechanisms　is　paramount.　In　this　paper,　we　propose　a　union　feed-in　tariff　framework　for　wind-solar-hydroelectric-thermal　power　generation.　Initially,　we　develop　a　wind-solar-hydroelectric-thermal　comprehensive　cost　model　considering　both　local　consumption　within　the　province　and　cross-border　transaction.　Subsequently,　we　delve　into　the　design　principles　of　the　union　feed-in　tariff,　ensuring　a　reasonable　rate　of　return　while　accommodating　the　diverse　influencing　factors　of　different　power　sources.　Our　approach　encompasses　the　formulation　of　feed-in　tariffs　for　local　consumption　within　the　province　and　cross-border　transaction.　Finally,　we　present　an　empirical　analysis　focused　on　Sichuan　province,　illustrating　the　application　of　our　framework,　particularly　in　the　context　of　the　Yazhong　Jiangxi　±800　kV　ultrahigh　voltage　direct　current　project.　Through　this　analysis,　we　derive　local　consumption　within　the　province　feed-in　tariff　values　and　cross-border　transaction　feed-in　tariff　values.　©　2024　Systems　Engineering　Society　of　China.　All　rights　reserved.